import java.util.Scanner;

/**
 * Created with Intellij IDEA.
 * Description:
 * User:Lenovo
 * Date:2024-12-12
 * Time:19:48
 */
public class Text {
    public static int fun(int n){
        if(n==1||n==2){
            return 1;
        }else {
            return fun(n-1)+fun(n-2);
        }
    }
    public static void main(String[] args) {
        Scanner san = new Scanner(System.in);
        int a = fun(san.nextInt());
        System.out.println(a);
    }
}
